/Engine/Source/Runtime/Engine/Classes/Materials/Material.h
Recursively update the bRealtimePreview for each expression based on whether it is connected to something that is time-varying. This is determined based on the result ofUMaterialExpression::NeedsRealtimePreview();
void RecursiveUpdateRealtimePreview ( [UMaterialExpression](API\Runtime\Engine\Materials\UMaterialExpression) * InExpression, [TArray](API\Runtime\Core\Containers\TArray)< [UMaterialExpression](API\Runtime\Engine\Materials\UMaterialExpression) * > & InOutExpressionsToProcess )